drag racing the breakout..rpm limits?

[dieselbeef]

factory cuts in about 5200 seems like...feels like im leaving some top end on the table by shifting at 5k..can i raise it...easily done with the power vision but

at what point do you think the flow will drop off...

stock heads..high flow intake...bassini 2 into 1..power vision map..

dont wanna wring it out but another 500 maybe? set it to 5700?

[dieselbeef]

wht is the biggest limting factor?

when does the air flow stall

[rigidthumper]

Air flow stall is from whatever is the restriction (choke point) of the system. Stock heads do not pull well above 5K, stock cams peak right at 5000 +/- 200 (depends on pipe).
I set shift light 5-7% above HP peak, so my shift is done by 10% past HP peak, trying to stay within 10% above/below peak power.

[kd]

   One of the times a dyno sheet WFO run is useful. It is also helpful to know and understand the RPM drop for each gear change. Like Rigid states, keeping the shift point in the power range (and therefore the running RPM) produces max effort. 

[turboprop]

factory cuts in about 5200 seems like...feels like im leaving some top end on the table by shifting at 5k..can i raise it...easily done with the power vision but

at what point do you think the flow will drop off...

stock heads..high flow intake...bassini 2 into 1..power vision map..

dont wanna wring it out but another 500 maybe? set it to 5700?

That Power Vision has the capability to log RPM. This is a really great tool and how the the big boys tune their clutch springs/weights and shift RPMs. It would be very helpful to you to have the capability in your pit to download rpm data (and AFR) and adjust the tune in between passes. Anything less than this is simply a guess in the dark. You must have data to do this properly.

If you do actually follow through and do this, what you are looking for is RPM drop between shifts. The same RPM will not be ideal for shifting into every gear. 1st gear will typically be happier with a higher RPM shift point than 3rd gear will. Key to this entire process is consistency. The ability to shift quickly and repeatedly without an air or electric shifter is critical.

[dieselbeef]

great advice thanks turbo...not ready for an air shifter yet...gonna mess around test tune til i ge comfy and do some bracket racing so yea..consistency is key

seems like tho from what rigid said...not alot to be gained but raising the rev limiter...

i will try making 2 passes and avg them..the adj it higher and see if et or mph change

shift light is at 5k right now....i think it interrupts at 52 stock


you guys seem to have exp..thanks....btw..its a 17 103

[turboprop]

great advice thanks turbo...not ready for an air shifter yet...gonna mess around test tune til i ge comfy and do some bracket racing so yea..consistency is key

seems like tho from what rigid said...not alot to be gained but raising the rev limiter...

i will try making 2 passes and avg them..the adj it higher and see if et or mph change

shift light is at 5k right now....i think it interrupts at 52 stock


you guys seem to have exp..thanks....btw..its a 17 103

Everything changes on the drag strip, even throughout the day as the air changes, track temp changes and track prep changes. Your oem clutch is another variable as very few oem clutch packs have the same characteristics under full load. The guys that are going fast on relatively stock bikes have spent many passes collecting data and dialing everything in.

As for that rev limiter, the goal is to shift at an RPM that puts the mid shift drop in the RPM zone that provides the most acceleration. I am going to go ut on a limb and say there will be measurable advantages to changing the rev limit to facilitate gear changes at the optimum RPM.

[dieselbeef]

i understand bracket racing..ive done it in a car...never drag raced a bike tho..i know dial ins and weathe changes as it cools off and stuff....even tho its bracket racing always wanna go as fast as possible

[guppymech]

I've read the TC B engine shouldn't be reved above 6k because of the balancers.

[itsafatboy]

its because of the balancers on the softail , id put it at 6200 and call it good?  or atleast 5800

[98fxstc]

great advice thanks turbo...not ready for an air shifter yet...gonna mess around test tune til i ge comfy and do some bracket racing so yea..consistency is key

seems like tho from what rigid said...not alot to be gained but raising the rev limiter...

i will try making 2 passes and avg them..the adj it higher and see if et or mph change

shift light is at 5k right now....i think it interrupts at 52 stock


you guys seem to have exp..thanks....btw..its a 17 103

Everything changes on the drag strip, even throughout the day as the air changes, track temp changes and track prep changes. Your oem clutch is another variable as very few oem clutch packs have the same characteristics under full load. The guys that are going fast on relatively stock bikes have spent many passes collecting data and dialing everything in.

As for that rev limiter, the goal is to shift at an RPM that puts the mid shift drop in the RPM zone that provides the most acceleration. I am going to go ut on a limb and say there will be measurable advantages to changing the rev limit to facilitate gear changes at the optimum RPM.

so just past max torque ?

[Hillside Motorcycle]

No need to spool an engine into an area where the power isn't.